1. Field of the Invention
This invention relates to a safe/arm device for controlling the firing of explosive charges, and more particularly to electronic safe/arm firing devices having internal power supplies.
It is currently commonplace to employ electronic safe/arm circuitry to control the firing of explosive charges such as those used in ordnance. Such circuitry often comprises isolation transformers between a power source and the detonator to inhibit the firing of the explosive charge in the event that the power source is inadvertently directly connected to the detonator. However, the prior art devices fail to teach how to safely power the firing circuitry that controls the firing of the device.
2. Related Art
U.S. Pat. No. 4,700,263 to Marshall et al, dated Oct. 13, 1987 discloses a safe/arm system in which a low power source (10) charges a bank of capacitors (C1)-(C8). After a suitable delay determined by a microprocessor (13), the charge stored in the capacitors is stepped-up through a transformer (T1) to charge a high-voltage capacitor (12) in a step-wise manner. When sufficiently charged, capacitor (12) initiates a munition charge by means of an exploding foil or exploding bridgewire. The capacitors do not power the microprocessor, and there is no firing switch operated off the transformer.
U.S. Pat. No. 4,651,646 to Foresman et al, dated Mar. 24, 1987 discloses a safe and arm circuit for use with a slapper detonator. In this circuit, a capacitor (32) is charged from a power source such as an air generator (30). The voltage from the capacitor (32) is stepped-up through a flyback transformer (35) through a switch (33) controlled by a microprocessor (37). Thus, the power from capacitor (32) is stepped-up to charge a detonator capacitor (40). At the desired time, microprocessor (37) actuates a switch (42) to fire the slapper detonator using the high-voltage stored in detonator capacitor (40). There is no teaching with respect to the source of power for the microprocessor.
U.S. Pat. No. 4,136,617 to Fowler, dated Jan. 30, 1979 discloses an electronic delay detonator in which an arming signal is applied to a safety circuit which steps-down the voltage and charges a firing circuit capacitor. When a firing pulse is applied to a triggering circuit, the timer is initiated, and after the selected time period, the timer sends a firing signal to the firing circuit to allow the firing capacitor to discharge through the detonator. There is no internal source of power for the circuitry that controls the charging and firing of the circuit.